Thanks for taking the time to report this bug and helping to make Ubuntu better.
For my own test on a natty server, I started with a 30G qcow2 disk with a lucid install on it. It had about 1G allocated. Conversion from qcow2 to raw took probably less than 10 seconds. Conversion back to qcow took a lot longer (perhaps a minute). So for a full 40G allocated drive I certainly would expect it to be slow. However you certainly do seem to have a real problem there. In your CurrentDmesg, I see [257894.409748] Buffer I/O error on device dm-9, logical block 0 [257894.409786] Buffer I/O error on device dm-9, logical block 0 This could indicate a real problem, or just a device which you've since removed (i.e. usb thumb drive). Could you look under /sys/block/dm-9 for more information? Can you look for relevant info in /var/log/syslog from this event and paste them here? Finally, could you re-test with the qemu-kvm package from the server- edgers's archive (see https://launchpad.net/~ubuntu-server- edgers/+archive/server-edgers-qemu-kvm)? ** Changed in: qemu-kvm (Ubuntu) Status: New => Incomplete -- You received this bug notification because you are a member of Ubuntu Server Team, which is subscribed to qemu-kvm in ubuntu. https://bugs.launchpad.net/bugs/712392 Title: qemu-img convert blocks other tasks -- Ubuntu-server-bugs mailing list Ubuntu-server-bugs@lists.ubuntu.com Modify settings or unsubscribe at: https://lists.ubuntu.com/mailman/listinfo/ubuntu-server-bugs